a piece of DNA (gene) is used to make a functional protein. List and describe each step in this
process, starting with the gene and ending with the folded protein
The process of making a functional protein from a gene involves several steps. Here is a description of each step:
1. Transcription: The first step is the transcription of the gene. The DNA double helix unwinds, and the enzyme RNA polymerase binds to the specific gene sequence. RNA polymerase then synthesizes a complementary strand of mRNA (messenger RNA) based on the template of the gene. This mRNA contains the information transcribed from the gene.
2. RNA Processing: Once the mRNA molecule is synthesized, it undergoes several modifications. The primary mRNA molecule contains both exons (coding regions) and introns (non-coding regions). The introns are removed through a process called splicing, resulting in a mature mRNA molecule consisting only of exons. Additionally, a protective cap (methylguanosine) is added to the 5' end of the mRNA, and a poly-A tail is added to the 3' end. These modifications stabilize the mRNA and facilitate its export from the nucleus.
3. mRNA Export: The mature mRNA molecule is then exported from the nucleus to the cytoplasm through nuclear pores. This step allows the mRNA to reach the ribosomes, where protein synthesis occurs.
4. Translation: In the cytoplasm, the mRNA binds to a ribosome, initiating the translation process. Translation involves the synthesis of a protein by assembling amino acids in the correct order based on the codons present in the mRNA. The ribosome reads the mRNA's genetic code in groups of three nucleotides called codons, and each codon specifies a particular amino acid. Transfer RNA (tRNA) molecules carry the corresponding amino acids and bind to the codons on the mRNA at the ribosome.
5. Protein Folding: Once the elongation phase of translation is completed, the newly synthesized chain of amino acids, called a polypeptide, undergoes folding. The folding process is guided by various cellular factors, including molecular chaperones. Proteins fold into specific 3D structures dictated by their amino acid sequence. This folding process is crucial for the protein's functionality, as misfolded proteins may be non-functional or even result in diseases.
6. Post-Translation Modifications: After folding, the protein may also undergo post-translational modifications. These modifications include the addition of functional groups, such as phosphate or sugar moieties, or the cleavage of specific sections to activate the protein. These modifications can further contribute to the functionality and stability of the protein.
Overall, the process of making a functional protein from a gene involves transcription, RNA processing, mRNA export, translation, protein folding, and post-translation modifications. Each step is essential in ensuring the proper synthesis and functionality of the protein.